1. Field of the Disclosure
The disclosed subject matter relates generally to computing systems and, more particularly, to a method and apparatus for implementing a machine instruction using a peripheral device.
2. Description of the Related Art
Computer processors employ various computational resources to implement machine instructions embodied in software. A machine instruction received by a central processing unit (CPU) core is decoded and provided to an execution unit for implementation. The execution unit uses microcode instructions to translate machine instructions into sequences of detailed circuit-level operations. Thus, the microcode serves as a bridge between the machine instructions, which may be the same for any number of CPU micro-architectures, and the specific circuit-level operations that are implemented by the CPU core to achieve the result intended by the machine instruction. Generally, microcode is customized to a particular processor micro-architecture.
In some cases it may be difficult to implement a particular machine instruction using microcode due to the complexity of the required operations. In such cases, it may be useful to employ an external computational resource for performing the actual calculations required to implement the machine instruction. In this context, external implies external to the CPU core containing the execution unit. The external computing resource may also be external to the integrated circuit device implementing the CPU core, or it may be part of the same integrated circuit device.
Various topologies exist for interfacing the processor core with an external computational resource. In one example, a dedicated communication bus may be provided between the CPU core and the external computational resource. Providing a dedicated bus increases the complexity of the system and generally increases cost. In another example, an existing public communication bus in the computer system may be employed for communicating with the external computational resource. The use of a public bus provides security challenges as a malicious entity may monitor the public bus and possibly interfere with the communication on the public bus.
The use of the same reference symbols in different drawings indicates similar or identical items.